NSString *text = @"good bad ask com good fault good";
    NSError *error;
    NSRegularExpression *regular = [[NSRegularExpression alloc] initWithPattern:@"good" options:NSRegularExpressionCaseInsensitive error:&error];
    if (!error) {
        NSArray *results = [regular matchesInString:text options:NSMatchingReportProgress range:NSMakeRange(0, text.length)];
        NSLog(@"%@", results);
    }
    else {
        NSLog(@"%@", error);
    }

这里有一个不错的教程http://www.cocoachina.com/ios/20150415/11568.html